c++基础学习（12）--（多线程、Web编程）

目录

1.多线程

#include <iostream>
// 必须的头文件
#include <pthread.h>

using namespace std;

#define NUM_THREADS 5

// 线程的运行函数
void* say_hello(void* args)
{
    cout << "Hello Runoob！" << endl;
    return 0;
}

int main()
{
    // 定义线程的 id 变量，多个变量使用数组
    pthread_t tids[NUM_THREADS];
    for(int i = 0; i < NUM_THREADS; ++i)
    {
        //参数依次是：创建的线程id，线程参数，调用的函数，传入的函数参数
        int ret = pthread_create(&tids[i], NULL, say_hello, NULL);
        if (ret != 0)
        {
           cout << "pthread_create error: error_code=" << ret << endl;
        }
    }
    //等各个线程退出后，进程才结束，否则进程强制结束了，线程可能还没反应过来；
    pthread_exit(NULL);
}

#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define NUM_THREADS     5

struct thread_data{
   int  thread_id;
   char *message;
};

void *PrintHello(void *threadarg)
{
   struct thread_data *my_data;

   my_data = (struct thread_data *) threadarg;

   cout << "Thread ID : " << my_data->thread_id ;
   cout << " Message : " << my_data->message << endl;

   pthread_exit(NULL);
}

int main ()
{
   pthread_t threads[NUM_THREADS];
   struct thread_data td[NUM_THREADS];
   int rc;
   int i;

   for( i=0; i < NUM_THREADS; i++ ){
      cout <<"main() : creating thread, " << i << endl;
      td[i].thread_id = i;
      td[i].message = (char*)"This is message";
      rc = pthread_create(&threads[i], NULL,
                          PrintHello, (void *)&td[i]);
      if (rc){
         cout << "Error:unable to create thread," << rc << endl;
         exit(-1);
      }
   }
   pthread_exit(NULL);
}

#include <iostream>
#include <cstdlib>
#include <pthread.h>
#include <unistd.h>

using namespace std;

#define NUM_THREADS     5

void *wait(void *t)
{
   int i;
   long tid;

   tid = (long)t;

   sleep(1);
   cout << "Sleeping in thread " << endl;
   cout << "Thread with id : " << tid << "  ...exiting " << endl;
   pthread_exit(NULL);
}

int main ()
{
   int rc;
   int i;
   pthread_t threads[NUM_THREADS];
   pthread_attr_t attr;
   void *status;

   // 初始化并设置线程为可连接的（joinable）
   pthread_attr_init(&attr);
   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

   for( i=0; i < NUM_THREADS; i++ ){
      cout << "main() : creating thread, " << i << endl;
      rc = pthread_create(&threads[i], NULL, wait, (void *)&i );
      if (rc){
         cout << "Error:unable to create thread," << rc << endl;
         exit(-1);
      }
   }

   // 删除属性，并等待其他线程
   pthread_attr_destroy(&attr);
   for( i=0; i < NUM_THREADS; i++ ){
      rc = pthread_join(threads[i], &status);
      if (rc){
         cout << "Error:unable to join," << rc << endl;
         exit(-1);
      }
      cout << "Main: completed thread id :" << i ;
      cout << "  exiting with status :" << status << endl;
   }

   cout << "Main: program exiting." << endl;
   pthread_exit(NULL);
}

当上面的代码被编译和执行时，它会产生下列结果：
main() : creating thread, 0
main() : creating thread, 1
main() : creating thread, 2
main() : creating thread, 3
main() : creating thread, 4
Sleeping in thread
Thread with id : 4 …exiting
Sleeping in thread
Thread with id : 3 …exiting
Sleeping in thread
Thread with id : 2 …exiting
Sleeping in thread
Thread with id : 1 …exiting
Sleeping in thread
Thread with id : 0 …exiting
Main: completed thread id :0 exiting with status :0
Main: completed thread id :1 exiting with status :0
Main: completed thread id :2 exiting with status :0
Main: completed thread id :3 exiting with status :0
Main: completed thread id :4 exiting with status :0
Main: program exiting.

#include <iostream>

#include <thread>

std::thread::id main_thread_id = std::this_thread::get_id();

void hello()  
{
    std::cout << "Hello Concurrent World\n";
    if (main_thread_id == std::this_thread::get_id())
        std::cout << "This is the main thread.\n";
    else
        std::cout << "This is not the main thread.\n";
}

void pause_thread(int n) {
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "pause of " << n << " seconds ended\n";
}

int main() {
    std::thread t(hello);
    std::cout << t.hardware_concurrency() << std::endl;//可以并发执行多少个(不准确)
    std::cout << "native_handle " << t.native_handle() << std::endl;//可以并发执行多少个(不准确)
    t.join();
    std::thread a(hello);
    a.detach();
    std::thread threads[5];                         // 默认构造线程

    std::cout << "Spawning 5 threads...\n";
    for (int i = 0; i < 5; ++i)
        threads[i] = std::thread(pause_thread, i + 1);   // move-assign threads
    std::cout << "Done spawning threads. Now waiting for them to join:\n";
    for (auto &thread : threads)
        thread.join();
    std::cout << "All threads joined!\n";
}

2.web编程